The present invention relates to an intercooler for a supercharger that provides supercharging air to a 4-cycle engine mounted in a small planing boat such as a motorboat or a recreational watercraft.
A small planing boat, which is often operated with the throttle wide open or in an idling state, unlike an automobile, is conventionally mounted with a 2-cycle engine in consideration of the acceleration of the engine and the like, as disclosed in Japanese Unexamined Patent Publication No. H 10-258794. However, a small planing boat must be mounted with a 4-cycle engine in order to increase its cruising distance and to achieve reduced engine vibration, and it is essential to install a supercharger in order to improve the engine air intake rate when mounting the small planing boat with a 4-cycle engine.
When a supercharger is utilized, the temperature of the supercharging air output from the supercharger rises to approximately 120xc2x0 C.xcx9c130xc2x0 C. due to the temperature increase caused during the compression at the compressor and the heat transmitted from the exhaust gas on the turbine side, and if the supercharging air is directly supplied to the cylinder, knocking will occur readily and only a small improvement in output can be achieved due to the lowered air density. Accordingly, a water-cooled intercooler such as that disclosed in Japanese Unexamined Patent Publication No. H 4-32694 or Japanese Unexamined Patent Publication No. H 4-208391 is provided to increase the air density by cooling the supercharging air for higher supercharger efficiency.
However, there is a problem with these intercoolers in that since the cooling water pipeline undergoes repeated expansion/contraction as the temperature of the intake air changes, the area over which the cooling water pipeline is connected with the casing is subjected to considerable stress, resulting in distortion occurring in the area, which, in turn, will cause cracks readily.
Accordingly, in the intercooler disclosed in Japanese Unexamined Utility Model Publication No. H 5-57318, an assembly constituted by securing the leading end and trailing end of the pipeline through which a fluid used to cool the intake air flows, to a supporting member and folding back the middle portion of the pipeline is housed in the casing with a gap between the folded portion and the casing so as to absorb the expansion/contraction of the cooling water pipeline at the gap.
However, the intercooler disclosed in Japanese Unexamined Utility Model Publication No. H 5-57318 poses a problem in that the cooling water pipeline, which is folded back, cannot have a large diameter and thus, the flow passage resistance at the pipe is bound to be high. In addition, if the pipe is folded back at the exact halfway point to form two half portions having flow path lengths equal to each other, the ease of pipe installation is compromised and more wasted space is created, whereas if the pipe is folded back to form two portions with different flow path lengths for ease of installation, the temperature distribution over the cooling area becomes inconsistent, resulting in a lower heat exchanging rate.
Accordingly, an object of the present invention is to provide an intercooler assuming a simple structure, that is capable of cooling supercharging air and absorbing expansion/contraction of the cooling water pipe and the casing caused by the heat of the supercharging air.
In order to achieve the object described above, in the intercooler according to the present invention comprising a heat exchanger constituted of at least a pair of tanks, a plurality of tubes communicating between the pair of tanks, a plurality of fins provided along the tubes over specific intervals and cylindrical intake/outlet pipes each communicating with one of the tanks and extending outward from the tank and a case defining a cooling space in which the heat exchanger is housed and through which supercharging air passes, a pair of cylindrical pipe insertion portions at each of which one of the intake/outlet pipes is inserted and is allowed to extend to the outside are formed at the case, and seal members each provided at one of the pipe insertion portions, constituted of an elastic material formed in a staged cylindrical shape that includes a first cylindrical portion placed in complete contact with the external circumferential surface of the respective pipe insertion portion and a second cylindrical portion placed in complete contact with the external circumferential surface of the intake/outlet pipe, seal the gaps between the intake/outlet pipes and the pipe insertion portions and are also utilized to fit the heat exchanger in the case with a gap.
Since the intake/outlet pipes of the heat exchanger housed inside the cooling space formed inside the case are inserted at the cylindrical pipe insertion portions formed at the case and the seal members each constituted of an elastic material formed in a staged cylindrical shape having the first cylindrical portion placed in complete contact with the pipe insertion portions and the second cylindrical portion placed in complete contact with the intake/outlet pipe seal the gap between the intake/outlet pipes and the insertion portions and fit the heat exchanger at the case with a gap as described above, the expansion/contraction of the heat exchanger and the case induced by heat can be absorbed at the seal members, and thus, the object described above is achieved.
In addition, it is desirable that the first cylindrical portion and the second cylindrical portion of each seal member be secured to the pipe insertion portion or the intake/outlet pipes by a ring clamp, so as to improve the seal and security of the seal members themselves.
It is also desirable that the intake/outlet pipes extend from the tanks to the outside along the direction in which the axis of the tubes extends and that the case can be divided along the axial direction. These structural features facilitate the process of mounting the heat exchanger in the case.
Furthermore, it is desirable that a buffer member constituted of an elastic material be provided between each tank of the heat exchanger and the inner surface of the case and that the buffer member include a side surface buffer member provided between the side surface of the tank and the inner surface of the case and an end surface buffer member provided between the end surface of the tank, i.e., one of the two tank ends set at the two ends along the direction in which the intake/outlet pipes extend and the inner surface of the case. Since the side surface buffer members provided between the side surfaces of the tank and the inner surface of the case secure the heat exchanger along the short side of the case and the end surface buffer members provided between the tank end surfaces at the two ends along the direction in which the intake/outlet pipes extend and the inner surface of the case secure the heat exchanger within the case along the longer side of the case, the heat exchanger can be secured to the case with a high degree of reliability while allowing the expansion/contraction of the heat exchanger and the case to be absorbed effectively.
Moreover, the case should preferably be formed by using a material whose main constituent is aluminum and the pair of tanks and the intake/outlet pipes of the heat exchanger should be formed by using a synthetic resin. It is also desirable to form each of the pair of tanks and the corresponding intake/outlet pipe communicating with the tank at the heat exchanger as an integrated unit by using a synthetic resin material. The use of these materials will improve the corrosion resistance of the intercooler and also facilitate the formation of the heat exchanger.